In the operation of wells it is often desirable to know the downhole condition of a well surface such as a well liner or well casing. For example, it is important to know if the casing or the liner is cracked. Similarly, the extent of liner slot plugging and perforation size or absence is also useful information. This type of well information can be obtained by the use of impression packers. An impression packer is a device which is run down a well to a location from where information is desired and then an impression element is pressed against the well surface by suitable means, usually an inflatable packer, to take an impression of the well surface. The impression element is removed from the well surface usually by deflating the inflatable packer and then removed from the well for inspection.
The above cross-referenced applications relate in part to suitable impression elements and to suitable inflatable packers for use in running an impression element in a well. The inflatable packers described in the applications filed prior to the filing date of the present application, however, and those heretofore used in the prior art have been run on a tubing string made of a number of tubing sections coupled together. The tubing string provides a conduit from the surface to the packer into which a fluid is injected down the well and into the packer to inflate it. The tubing string conduit is also used to deflate the packer. In the crudest form, this is done simply by releasing the pressure on the packer by venting the tubing string to atmosphere. In more sophisticated systems, the packer may be deflated by a downhole device which can be triggered by dropping a sinker bar or a similar weight from the surface down the tubing string. A drawback to the use of a tubing string for running inflatable packers, however, is the time and trouble of making up the tubing string from a plurality of tubing sections which must be successively coupled together at the surface as the tubing string is formed and lowered into the well. A well pulling rig is also needed to run and pull the tubing string.
In order to dispense with the use of the tubing string, it has been found desirable to develop an inflatable packer which can be run on wire line and which needs no operational connection such as a tubing string or an electrical line to the surface. However, as noted, when the inflatable packer is used to carry an impression sleeve into the well to obtain impressions therefrom, certain problems are encountered. Thus, the impression sleeve must be first lowered into the well to a depth where information is needed prior to inflating the packer to cause the impression sleeve to contact the well surface. Additionally, it is usually desirable to have the impression sleeve contact the well surface for a predeterminable time at a predeterminable pressure before deflating the packer and removing the packer carrying the impression sleeve from the well. In addition to these problems, a wire line inflatable packer must be entirely self-contained, which necessitates carrying with the packer a source of high-pressure gas for inflation use. The present invention is directed to solving these problems and thus providing an efficient and reliable wire line inflatable packer which is useful in making impression packer runs in wells.